Conventionally, as an electronic device manufactured by mounting electronic components such as a connector on a printed circuit board, a device having an insertion-mounting structure is known. In this structure, a terminal of an electronic component is inserted in a through hole of a printed circuit board, and the terminal is solder-bonded to a land provided on a wall surface and a periphery of the opening of the through hole, for example, disclosed in JP-2005-327643A. Further, an electronic device having a surface mounting structure is known. In this structure, a terminal of an electronic component is solder-bonded to a land provided on the surface of a printed circuit board, for example, disclosed in JP-2006-256448A corresponding to U.S. Pat. No. 7,192,313, FIG. 12.
In the case of an electronic device having the insertion-mounting structure, it is necessary to perform flow soldering (including local flow) using molten solder jet flow. In the printed circuit board, on the rear surface of electronic component mounting surface, an area exposed to the molten solder and an area interfering with a nozzle to jet-flow the molten solder are not employed as an electronic component mounting area. That is, as the area in which electronic-component mounting is disabled is large, the electronic component packaging density cannot be improved without difficulty in the whole (both surfaces) of the printed circuit board.
In the case of the electronic device having the surface mounting structure, as flow soldering is not required, the electronic component packaging density can be improved. However, as reflow process is performed while a terminal is placed on a corresponding land, in a status before the solder is cooled and solidified (molten solder status), a positional shift often occurs between the terminal and the corresponding land. For example, upon reflow process, when deformation (warp or the like) occurs in the printed circuit board (housing of the electronic component) due to a difference between linear expansion coefficients of the printed circuit board and the electronic component, there is a probability of positional shift between a terminal and a land or falling of the terminal from the land. Further, in accordance with increase in the number of terminals, it becomes difficult to ensure co-planarity in connection portions between the terminals and the lands. Further, it is further difficult to ensure connection all the terminals and corresponding lands due to the influence of warp of the printed circuit board or the like. That is, this structure has a problem in the point of connection reliability.
On the other hand, JP-11-111407A corresponding to U.S. Pat. No. 6,081,998 (especially in FIGS. 14 to 17) discloses a connector which has a lead pin (branch terminal) having an end (insertion member) which can be inserted in a hole (through hole) in a printed circuit board and a soldering member (surface member) formed in a position away from the end by a predetermined distance. Further, JP-11-317265A discloses a print wiring board mounting structure integrally having a horizontal projection (surface member) bonded to the surface of a lead connecting land (surface land) of a printed wiring board (printed circuit board) and a vertical projection (insertion member) inserted in a through hole of the printed wiring board, at an end of a lead (branch terminal) of an electronic component. In these applications, reflowing on the insertion member is not required. The surface member is solder-bonded to the corresponding surface land while the insertion member is inserted in the through hole.
However, in JP-11-111407A and JP-11-317265A, in the terminal, an end area of a portion extended from the connector housing in approximately vertical state with respect to the printed circuit board is employed as the insertion member, and a portion extending from the portion approximately vertical to the printed circuit board, in approximately parallel to the flat surface of the printed circuit board is employed as the surface member. That is, the surface member forming the branch terminal and the insertion member form an L-shaped structure. In this L-shaped structure, a side fillet is formed only in one position of the end of the surface member. Further, the amount of positional shift with the insertion member as a rotational axis is large. To ensure connection reliability, the packaging density may be lowered.
Further, in JP-11-111407A, as the insertion member is not solder-bonded, to ensure desired connection reliability, it is necessary to increase the surface member to increase a contact area with respect to the solder. Accordingly, in the point of electronic component packaging density on the electronic component mounting side, by extension, in the point of entire (both surfaces) circuit board, the electronic component packaging density cannot be improved without difficulty.
Further, in JP-11-317265A, the inner surface of the through hole is coated with conductive material, and the insertion member is inserted in the through hole such that the end of the insertion member is exposed on the rear surface side of the connector mounting surface of the printed circuit board. In this structure, a large amount of solder on the surface land flows in the through hole by the capillary phenomenon. Accordingly, a fillet (side fillet) cannot be excellently formed on the surface member in accordance with size of the surface land. Further, voids (bubbles) might be formed in the solder flowed in the through hole. To avoid this problem (to ensure connection reliability), it is necessary to increase the surface land (surface member). Also, the electronic component packaging density cannot be improved without difficulty.
Thus, it is required for the electronic device capable of improvement in connection reliability and packaging density.
Further, an electronic device, in which electronic components such as a connector having plural terminals arrayed along the surface of a printed circuit board are reflow-mounted on the printed circuit board having lands with respect to a main body formed of insulating material, is known. As such electronic device, JP-11-317265A and JP-7-153508A (including FIG. 4) disclose an electronic device in which electronic components are reflow-mounted on a printed circuit board having plural lines of lands provided along an array direction of terminals. By using this structure, the main body can be downsized in the array direction of the terminals.
However, according to JP-11-317265A and JP-7-153508A, a terminal connected with a land positioned away from the main body disturbs supply of reflowing heat to a terminal connected with a land positioned closer to the main body (junction with the land) than the above land. For example, in the structure disclosed in JP-7-153508A, the terminal has a structure where a portion on the side connected with the land is extended approximately parallel to the printed circuit board from the main body, and the end of the parallel portion is bent to be vertical to the surface of the printed circuit board, and a portion mounted on the land is provided at the end of the vertical portion. Further, the height of the parallel portion of the terminal connected with the land positioned away from the main body is high from the surface of the printed circuit board, and the length of extension from the main body is long. Accordingly, upon reflowing, the terminal connected with the land positioned away from the main body blocks heat to the terminal connected with the land closer to the main body, and connection reliability may be lowered in the junction (soldering failure may occur). Especially, in the array direction of the terminals, as the interval between adjacent terminals is narrow, the connection reliability may be lowered. Thus, it is required to improve connection reliability.